The Senate utility tunnels comprised an extensive 572-quadrant, bi-level tunnel system, built deep beneath the infrastructure, that delivered both water and air to the Senate Building on Coruscant.
The Senate air system was stacked on top of the water system, with linked passageways that allowed workers to commute between the two systems. Interactive orientation blueprints—laser-embossed schematics—of the Senate system could be found scattered throughout, upon walls, allowing workers to more easily access desired work areas and access points.
In 24 BBY, the air-tunnels were to be used as a delivery system for the Zone of Self-Containment drug by the galactic criminal Granta Omega and mad scientist Jenna Zan Arbor, as part of a plan to assassinate Supreme Chancellor Palpatine and thousands of Senators and their top advisors, but the plot was ultimately foiled by the Jedi (though not without casualties).
Behind the scenes
The Senate Utility Tunnels featured in the young adult novel Jedi Quest: The False Peace, the ninth volume in the Jedi Quest series written by Jude Watson. It has been the only appearance of the tunnels to date.